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1467 



TERTIARY FAUNA OF FLORIDA 



ternal; hinge of three cardinals in the right valve, of which the posterior is 

 more or less effaced by the resilium, and two in the left valve; the anterior 

 edge of the right and the posterior edge of the left hinge-margin grooved to 

 receive the edge of the opposite valve, which is bevelled to serve as a lateral 

 lamina; sculpture chiefly concentric and often obsolete except near the um- 

 bones. 



Section Crassatellites s. s. 



Valves with the nepionic shell convex; the adult more or less trigonal or 

 quadrate, the third right cardinal usually perceptible below the scar of the 

 resilium, the inner margins of the valves usually crenate. 



Pachythcerus Conrad, 1869, and Crassitina Weinkauff, 1881, are synony- 

 mous. 



Section Scambula Conrad, 1869 (emended). Type S. subplana Con- 

 rad. 



Valves with the nepionic shell flattened, the adult usually elongated, the 

 third right cardinal obsolete or absent, the resilium large; the inner margins 

 of the valves rarely crenate but usually smooth. 



Subgenus Micromeris Conrad, 1866. Type Astarte minutissima Lea, 1833. 



Shell minute, triangular, radially sculptured with internally crenate mar- 

 gins ; resilium internal in front of the right posterior cardinal ; lateral margins 

 of the left valve fitting into grooves in the opposite margins of the right valve ; 

 anterior right cardinal obscure ; pallial line entire. Formula ^ *;*";* Ptero- 

 meris Conrad, 1865, not 1862, is synonymous. The type is from the Clai- 

 bornian and Lisbon Eocene. It is with some hesitation that I have left this 

 and the following group here instead of transferring them to the Condylo- 

 cardiidce. 



Subgenus Cuna Hedley, 1902. Type C. concentrica Hedley. Recent fauna of 

 Australia. 



Shell minute, trigonal, concentrically or radially sculptured, with crenate 

 internal margins ; resilium internal, behind the right posterior cardinal ; pos- 

 terior right and anterior left lateral margins fitting into sockets in the margin 

 of the opposite valve; posterior left cardinal obscure, sometimes obsolete; 

 pallial line entire ; dental formula L^E^ 1 ^ 1 , the anterior left and middle right 



R. i.onoioi.o 



cardinal teeth usually bifid or grooved. 



This group is represented by recent species in the fauna of Australia and 

 Japan and by one species in the Claibornian Eocene. It is very close to Micro- 



